1. Field of the Invention
The present invention relates to an apparatus for processing a photosensitive material with a processing liquid.
2. Description of the Background Art
Photosensitive materials, such as photosensitive films, photographic paper, printing plates and the like, on which images have been recorded are processed with a processing liquid such as activator, fixing solution, stabilizer, and rinsing water. Apparatuses for performing such processes upon photosensitive materials include a known dip-type processing apparatus wherein the photosensitive materials are fed into a processing tank storing a processing liquid by feeding means comprising pairs of feed rollers and the like and then dipped in the processing liquid, thereby subjected to processing.
Such an dip-type processing apparatus requires a great amount of processing liquid to dip the photosensitive materials therein. In the dip-type processing apparatus, the processing liquid is deactivated due to repeated processings for many photosensitive materials or developing degradation with time resulting from carbon dioxide and oxygen in the atmosphere. The processing liquid is recovered from the deactivation by adding a replenisher fluid to the processing liquid. This causes a difference between the ingredients of the processing liquid when the process starts and the ingredients of the processing liquid after a certain amount of process continues, failing to achieve exactly uniform processing.
To solve the problem, a coat-type photosensitive material processing apparatus has been used for coating a photosensitive surface of the photosensitive material with the processing liquid in amounts required to process the photosensitive material to perform processing in place of dipping the photosensitive material in the processing liquid. An example of the coat-type processing apparatus known in the art is such that the processing liquid is discharged from a processing liquid supply nozzle having a plurality of processing liquid discharge holes onto a roller (referred to hereinafter as a "roughened roller") having a surface roughened by forming grooves therein, and the roughened roller is rotated in contact with the photosensitive material, whereby the processing liquid is applied to the photosensitive material through the roughened roller.
In the background art processing apparatus, a pump for supplying the processing liquid by the application of pressure is used to force the processing liquid from a processing liquid tank storing the processing liquid into a processing liquid supply pipe having a plurality of processing liquid discharge holes. Since the pump is required to correctly supply a small constant amount of processing liquid per unit time, a pump for generating pulsation (referred to hereinafter as a "pulsation pump" in the present application) such as a peristaltic pump, an oscillating pump, and a bellows pump is used.
The background art apparatus has drawbacks to be described below.
1) For example, in the process step of coating a stabilizer to stabilize a lithographic printing plate employing a silver complex salt diffusion transfer reverse method (DTR method) after the development of the lithographic printing plat, the photosensitive layer of the photosensitive material has been swelled by the activator in the development step. When the swelled photosensitive material contacts the roughened roller of the background art apparatus, the photosensitive surface of the photosensitive material is damaged. PA1 2) The coat-type processing apparatus preferably uses a minimum amount of processing liquid in terms of running costs required for processing and environmental issues. However, supply of a small amount of processing liquid to the processing liquid supply nozzle makes it difficult for the background art apparatus to provide a uniform amount of processing liquid discharged from the processing liquid discharge holes to the roughened roller, accordingly resulting in a non-uniform amount of processing liquid applied to the photosensitive material. This phenomenon is liable to occur particularly in the leading edge portion of the photosensitive material. PA1 3) A processing liquid supply apparatus employing the pulsation pump repeats a discharging state wherein the processing liquid is discharged from the processing liquid discharge holes and a non-discharging state wherein the processing liquid is not discharged as the processing liquid delivered from the pulsation pump produces a pulsating flow. In the non-discharging state of the processing liquid, air is sometimes drawn into the processing liquid supply pipe through such a processing liquid discharge hole in the reverse direction to form an air bubble in the processing liquid supply pipe. If such a bubble in the processing liquid supply pipe is greater in size than the processing liquid discharge hole, the surface tension of the processing liquid defining the bubble causes the bubble to block the processing liquid discharge hole to preclude the processing liquid to pass through the discharge hole. This results in a non-uniform amount of processing liquid discharged from the plurality of processing liquid discharge holes of the processing liquid supply pipe. PA1 4) In the coat-type photosensitive material processing apparatus, when a puddle of processing liquid having a sufficient volume is not formed between the roughened roller and a support roller prior to the application of the processing liquid to the photosensitive material, processing unevenness resulting from the shortage of the processing liquid occurs particularly in a leading edge portion of the photosensitive material. PA1 5) The coat-type photosensitive material processing apparatus is intended to promote processing by supplying the processing liquid from a processing liquid tank for storing the processing liquid heated to a predetermined temperature to a processing liquid coating portion for coating the photosensitive material with the processing liquid to apply the heated processing liquid to the photosensitive material. At the start of coating of the photosensitive material, the temperatures of a feed passage of the processing liquid from the processing liquid tank to the processing liquid coating portion and the temperatures of the above described roughened roller and support roller have been decreased to room temperature. This decreases the temperature of the processing liquid to be applied to the photosensitive material through the processing liquid feed passage, resulting in processing unevenness. PA1 6) In the coat-type processing apparatus employing the roughened roller, contaminants such as silver sludge (referred to hereinafter as "silver sludge and the like") are produced from the processing liquid when the processing liquid is continuously applied to the photosensitive material. The silver sludge and the like is deposited in recesses, such as grooves, of the roughened roller.
Additionally, the use of the lithographic printing plate employing the silver complex salt diffusion transfer reverse method (DTR method) wherein development proceeds rapidly as the photosensitive material not only makes the above described drawback pronounced but also decreases printing performance, particularly the plate life, which is a problem inherent in the lithographic printing plate.
The non-uniform amount of processing liquid coating the photosensitive material creates processing unevenness of the developed photosensitive material. The occurrence of the processing unevenness is particularly pronounced in the lithographic printing plates utilizing the silver complex salt diffusion transfer reverse method (DTR method) in which development proceeds rapidly.
To solve this problem, there has been proposed a photosensitive material processing apparatus wherein the processing liquid is supplied from a slit opening formed between a pair of sheets to a processing liquid coating portion comprising a pair of non-rotatable rod-shaped members and the photosensitive material is passed through a puddle of processing liquid stored between the pair of rod-shaped members whereby the processing liquid is applied to the photosensitive material.
This photosensitive material processing apparatus is capable of relatively uniformly supplying a small amount of processing liquid. In this case, however, the amount of processing liquid coating the photosensitive material depends on the amount of processing liquid supplied to between the pair of rod-shaped members. Thus, the attempt to coat the entire photosensitive material with an exactly uniform amount of processing liquid has an inevitable limitation.
In the presence of the silver sludge and the like covering the recesses, such as grooves, of the roughened roller, the decrease in the amount of processing liquid to be applied to the photosensitive material causes the shortage or non-uniformity of the amount of processing liquid to be applied to the photosensitive material. The shortage or non-uniformity of the processing liquid to be applied to the photosensitive material results in the processing unevenness of the developed photosensitive material and the reduction in plate life in printing using the photosensitive material. Such phenomena are particularly pronounced when the lithographic printing plate employing the silver complex salt diffusion transfer reverse method (DTR method) wherein development proceeds rapidly is used as the photosensitive material.
Thus, an operator must repeatedly clean the roughened roller to remove the silver sludge and the like deposited on the roughened roller.